1. Field of the Invention
This invention relates to an improved inflatable lighter-than-air article, more particularly an improvement in a covering for an inflatable lighter-than-air article.
2. Prior Art
Although inflatable lighter-than-air articles such as balloons, dirigibles, zeppelins, and blimps have been known to man for a long time, they have never achieved their full potential as carriers of either cargo or passengers.
One of the reasons for this is the lack of a covering having sufficient lightness and strength which is capable of being manufactured inexpensively and easily.
Known coverings of inflatable lighter-than-air articles are comprised of biaxial weave fabrics coated with various resins or elastomers such as neoprene or urethane. Coating biaxial fabric is well known in the art. However, such coated fabrics have an inherent weakness of the bias (45.degree. from either the warp or weft yarns) which can lead to insufficient physical properties for inflatable articles. For example, tear and tear propagation resistance are physical poperties which generally can be inadequate. At the low coating weights required for airships, these coated fabrics may have good tear but have poor bias strengths. To achieve a balance of these properties it is necessary to laminate multiple plies of fabric oriented at different angles. To laminate in this manner requires a laborious process, part of which can only be done by hand.
Triaxial fabrics are described in U.S. Pat. No. 3,446,251, issued May 27, 1969 to Norris F. Dow. The stated resistance to tear of these fabrics is said to be a property for many end-use applications. However, there does not appear to be much difference in isotropic strength of uncoated triaxial fabrics when compared to uncoated biaxial fabrics of similar construction and weight.
An inflatable lighter-than-air article having the improved covering has reduced weight and increased strength, and allows the carrying of larger and heavier loads; thereby, increasing its safety, economic advantage, and acceptance. This would aid inflatable articles to achieve their full commercial potential.